x/mobile: Key codes don't include non-keypad Plus Sign

[justledbetter]

CodeKeypadPlusSign is returned by the library via this line, similar to CodeKeypadHyphenMinus above it:

https://github.com/golang/mobile/blob/c6794c95c70b02ddb1a79d92fec29f8b8ddd8836/event/key/key.go#L179

but there is no corresponding CodePlusSign with CodeHyphenMinus:

https://github.com/golang/mobile/blob/c6794c95c70b02ddb1a79d92fec29f8b8ddd8836/event/key/key.go#L136

[mknyszek]

CC @hyangah via https://dev.golang.org/owners

[justledbetter]

For reference, Key.Code seems to be set to decimal 46 when the non-keypad + is hit, and this works appropriately when combined with Key.Modifiers (Alt-+, Ctrl-+, etc) - As tested on a Cros linux container on ChromeOS 128.

[justledbetter]

Looking further at the code, it seems that the correct way to call this is to look for

(event.Modifiers&key.ModShift != 0) && (event.KeyCode == key.CodeEqualSign)

Tested this on the CrOS system I originally hit the problem on and this seems to be the right fix. No code change needed to x/mobile after all! 😄